Something else just came to mind about this -
That whole geographic thing should probably be REALLY taken into account. Lets say these things perform as designed/intended/etc, and a bunch of them were to be deployed. Over water or large spans of sparse ice, its probably not going to be an issue, but what happens when one of these things catastrophically fails (rotor/blade destruction/fire/whatever) and becomes earthbound? I see that the floatation devices are set up in cells, presumably to mitigate the negative effects of any single cell's failure. But isn't there a such thing as blades shattering into zillions of pieces, leading to more cells failing than it takes to keep it airborn?
Not trying to cut the idea off at the knees, but something about this is just a bit more than a head scratcher. Between planes possibly getting tangled in the tethering, and the risk of a whirling ball of pissed off turbine with an uncontrolled affinity for gravity, I'm not so sure the pros outweigh the cons.
Steve